The present invention relates to ionic compounds comprising a highly delocalized anionic charge, to a process for their preparation and to their uses.
It is well known that the salts of strong acids such as HClO4, HBF4, HPF6 and HRFSO3 (RF=perfluororadical) have properties in the field of electrochemistry and catalysis, but these properties are limited. The xe2x80x9csuperacidsxe2x80x9d obtained by adding a Lewis acid such as SbF5 to the abovementioned compounds are moreover known. However, these compounds are not stable other than in protonated form and in non-solvating media such as aliphatic hydrocarbons. The salts are unstable in the usual polar solvents.
Perfluorosulfonimide derivatives H[RFSO2NSO2RF] (RF=perfluoroalkyl) have been studied since quite recently. They have advantageous stability properties in protonated form or in the form of salts and are used as solutes in electrochemistry and as catalysts. However, it is not possible to give these salts all of the properties required for all the applications, in particular in terms of acidity, dissociation or solubility, since the use of compounds containing perfluoro chains of several carbons only slightly increases the acidity or the dissociation of the salts, when compared with the simplest compound RF=CF3, and induces rigidity in the molecule to the detriment of the conductivity properties. Long fluoro chains are both hydrophobic and oleophobic and do not allow any appreciable increase in the solubility in organic media. Replacement of the groups RF in the simple imides with non-perfluoro or only partially fluorinated groups reduces the acidity and the solubility substantially.
The aim of the present invention is to provide novel ionic compounds derived from perfluorosulfonimides in which the delocalization of the anionic charge is improved, thus resulting in markedly better acidity and dissociation than those of the known compounds, while at the same time retaining good stability.
Accordingly, a subject of the present invention is ionic compounds, their uses and a process for preparing them.
One compound according to the invention is an ionic compound corresponding to the formula 
in which:
Mm+ is a proton or a metal cation having the valency m, chosen from ions of alkali metals, of alkaline-earth metals, of transition metals or of rare-earth metals, or an organic onium cation or an organometallic cation, 1 less than m  less than 3;
X1 and X2, denoted below by Xi, represent, independently of each other, Sxe2x95x90Z3, Sxe2x95x90Z4, Pxe2x80x94R3 or Pxe2x80x94R4;
Q represents N, CR5, CCN or CSO2R5;
Z1, Z2, Z3 and Z4, denoted below by Zi, represent, independently of each other, xe2x95x90O, xe2x95x90NCxe2x89xa1N, xe2x95x90C(Cxe2x89xa1N)2, xe2x95x90NS(xe2x95x90Z)2R6 or xe2x95x90C[S(xe2x95x90Z)2R6]2, Z having the same meaning as Zi, it being understood that, in a segment xe2x80x94X1xe2x80x94Qxe2x80x94X2xe2x80x94, not more than 3 groups Zi represent xe2x95x90O;
R1, R2, R3, R4, R5 and R6, denoted below by Ri, represent, independently of each other, Y, YOxe2x80x94, YSxe2x80x94, Y2Nxe2x80x94 or F;
Y represents a monovalent organic radical, preferably containing from 1 to 16 carbon atoms, chosen from alkyl, alkenyl, oxaalkyl, oxaalkenyl, azaalkyl, azaalkenyl, aryl, alkylaryl or perfluoroalkyl radicals, or from the radicals obtained from the abovementioned radicals by substitution, in the chains and/or the aromatic part, with hetero atoms such as halogens, oxygen, nitrogen, sulfur or phosphorus; it being understood that is sulfur or phosphorus are present, they can optionally be linked to substituted oxygen or nitrogen atoms, or alternatively Y is a repeating unit of a polymeric frame.
When Mm+ is a metal cation, it can be an alkali et al (in particular Li+ and K+) , an alkaline-earth metal (in particular Mg++, Ca++ or Ba++) , a transition metal (in particular Cu++, Zn++ or Fe++) or a rare-earth metal (in particular Re+++).
When Mm+ is an onium cation, it can be chosen from ammonium ions [N(Yj)4]+, amidinium ions RC[N(Yj)2]2+, quanidinium ions C[N(Yj)2]3+, pyridinium ions [C5N(Yj)6]+, imidpazolium ions C3N2(Yj)5+ nium ions C3N2(Yj)7+, triazolium ions C2N3(Yj)4+, carbonium ions C5(Yj)5C+, NO+ (nitrosyl) or NO2+ ions, sulfonium ions [S(Yj)3]+, phosphonium ions [P(Yj)4]+ and iodonium ions [I(Yj)2]+. In the various abovementioned onium ions, the substituents Yj on the same anion can be identical or different. They represent, independently of each other, H or one of the substituents indicated above for Y.
When Mm+ is an organometallic cation, it can be chosen from metalloceniums. For example, mention may be made of the cations derived from ferrocene, from titanocene, from zirconocene, from an indocenium or from an arene metallocenium. It can also be chosen from metal cations coordinated by atoms such as O, S, Se, N, P or As, borne by organic molecules, in particular in the form of carbonyl, phosphine or porphyrine ligands optionally containing chirality. Mm+ can also be a cation derived from the alkyl groups defined for Y above and limited to those containing from 1 to 10 carbon atoms, for example a trialkylsilyl, tetraalkylgermanyl or dialkylstannyl derivative; in this case, M is linked to the group [R1xe2x80x94X1(Z1)xe2x80x94Qxe2x88x92xe2x80x94X2(Z2)xe2x80x94R2] via a very labile covalent bond and the compound behaves like a salt. The cation M can also be the repeating unit of a conjugate polymer in cationic oxidized form. As specific examples, mention may be made of the methylzinc, phenylmercury, trialkyltin or trialkyllead, chloro[ethylenebis(indenyl)]zirconium(IV) or tetrakis-(acetonitrile)palladium(II) cations. The organometallic cation can form part of a polymer chain.
The compounds according to the invention in which at least one of the groups Xi represents a phosphorous group are particularly advantageous for the great stability of the Pxe2x80x94N and Pxe2x80x94C bonds and for their flexibility. As a result, these compounds are more soluble and have a lower melting point than the sulfur-containing homologous compounds. Moreover, a large number of phosphorous compounds bearing two substituents R are commercially available or can readily be synthesized. For example, mention may be made of the compounds 
Mention may be made in particular of the phosphorous compounds in which Q represents N. 
The compounds in which the radicals Zi represent RFSO2N and those in which the radicals Ri represent a perfluoro group or an alkyl group are particularly advantageous, especially for the high acidity and the dissociation of the corresponding salts.
Among the compounds of the present invention corresponding to formula (I), mention may be made of those in which the groups Xi represent Sxe2x80x94Zi, more particularly those in which Q is N, and which correspond, respectively, to the formulae: 
One particular family of compounds according to the invention corresponds to formula (VII), given that if R1 is CF3, R2 is a phenyl optionally bearing a halogen or an NO2, three substituents Zi represent O and one substituent Zi represents xe2x95x90NSO2CF3, then M is other than an alkali metal cation or a proton.
Another family of compounds according to the invention corresponds to formula (I) in which the radicals R1 and R2 are chosen, independently of each other, from perfluoroalkyl radicals preferably containing from 1 to 8 carbon atoms, alkyl radicals preferably containing from 1 to 8 carbon atoms, alkenyl radicals preferably containing from 2 to 18 carbon atoms, dialkylamino radicals in which the alkyl radicals preferably contain from 1 to 18 carbon atoms, and styrenyl radicals. For example, mention may be made of the compounds corresponding to the following formulae, in which Rf represents a perfluoro radical, Q and M have the meaning given above, and Y, Yxe2x80x2, Yxe2x80x3, Yxe2x80x2xe2x80x3 and Yxe2x80x3xe2x80x3 have the meaning given above for Y: 
The compounds corresponding to formula (I), in which the groups Zi are chosen from xe2x95x90O, xe2x95x90Nxe2x80x94Cxe2x89xa1N and xe2x95x90C(Cxe2x89xa1N)2, constitute another advantageous family. The presence of one or more groups xe2x95x90Nxe2x80x94Cxe2x89xa1N or xe2x95x90C(Cxe2x89xa1N)2, makes it possible to increase the dissociation and the resistance to oxidation of the anion without substantially increasing its molar mass or its volume. For example, mention may be made of the following compounds: 
Mention may also be made in particular of the compounds corresponding to the formula (VII) 
in which three groups to Z1 to Z3 represent oxygen and Z4 represents xe2x95x90C[S(xe2x95x90Z)2R6]2. For example, mention may be made of the following compounds: 
Mention may also be made of the compounds corresponding to the formula 
in which the groups Ri, Zi and Q have the meaning given above, in particular compounds in which the groups Zi are O, and Q is N.
Mention may also be made of the compounds of formula 
in which the groups Rf and Rxe2x80x2f represent perfluoroalkyl radicals, the groups Zi and Ri have the meaning given above, in particular compounds in which the groups Zi are O, and Rf is CF3.
In general, the replacement of the oxygen in the SO2 end groups of 
with groups Z representing xe2x95x90NSO2Ri makes it possible to construct molecules of general formula: 
The choice of the substituents Ri in the compounds of the present invention makes it possible to obtain compounds in which the anion has intrinsic chirality on a sulfur atom. Such compounds are useful for inducing enantiomeric selectivity during the preparation of active organic compounds or for inducing stereoselectivity in polymerization reactions. Among these compounds, mention may be made of those corresponding to one or other of the following formulae [R1SO2Nxe2x80x94S*xe2x95x90O(R2)xe2x95x90NSO2R6]xe2x88x92 in which R1 is different from R6, or [R1SO2Nxe2x80x94S*xe2x95x90O(R2)xe2x95x90Nxe2x80x94S*xe2x95x90O(R5)xe2x95x90NSO2R6]xe2x88x92. The compounds most particularly preferred are those in which R1 and R6 represent, independently of each other, a radical chosen from F, CF3, C2F5, C4F9, C6F13 and C8F7, and R2 and R5 represent, independently of each other, an alkyl, an aryl, an alkylaryl or a dialkylamino preferably containing from 1 to 20 carbon atoms.
The ionic compounds of the present invention can be prepared by various processes.
In general, a compound corresponding to the formula 
is prepared by reacting a precursor compound, noted below (Z1,L) comprising the group Z1 and a leaving group L, with a derivative A2Z2 of the group Z2 according to one of the following reaction schemes: [R1xe2x80x94X1(Z1)xe2x80x94Qxe2x80x94X2(L)R2+A2Z2xe2x86x92R1xe2x80x94X1(Z1)xe2x80x94X2(L)(Z2)R2]xe2x88x92A++LA or R1xe2x80x94X1(Z1)xe2x80x94QA2+Lxe2x80x94X2(Z2)R2xe2x86x92[R1xe2x80x94X1(Z1)xe2x80x94X2(L)(Z2)R2]+A+LA
A represents an alkali metal, a proton, an amino or phosphorus-containing base, a trialkylsilyl group, a dialkylstannyl group, MgL1, ZnL1, CdL1, Cu, Mg, Zn, Cd, Hg or a trialkylsilyl, trialkylgermanyl or trialkylstannyl group.
The leaving groups L or L1 are advantageously chosen from halogens, pseudohalogens including fluoro or non-fluoro sulfonates, and imidazoyl, triazolyl and benzotriazoyl radicals.
The compounds (Z1,L) in which the leaving group is a halogen can be prepared, for example, by the action of a halogenating agent on a salt R1xe2x80x94X1(Z1)xe2x80x94Qxe2x80x94X2(O)(R2)xe2x88x92A+ or on the corresponding acid. The cation A is preferably chosen from alkali metal cations, inorganic ammonium ions NH4+ or organic ammonium ions R3NH+ (including pyridinium) and the Ag+ ion, which has strong affinity for Cl, Br and I.
Among the halogenating agents which are useful, mention may be made of SF4, trifluoro(diethylamino)sulfur IV (DAST), thionyl chloride, oxalyl chloride, oxalyl fluoride, phosphorus pentachloride, the mixture P"PHgr"3+CCl4, (chloromethylene)dimethylammonium chloride [CH(Cl)xe2x95x90N(CH3)2]+Clxe2x88x92 or its homologue derived from N-methylpyrrolidinone, and 1-methyl-2-fluoropyridinium iodide. The preparation of a compound (Z1,L) in which the leaving group is a halogen is illustrated schematically by the following example:
[CF3SO2NSO2(C4H9)]Na+(COCl)xe2x86x92CO+CO2+[CF3SO2NSO(C4H9)Cl]+NaCl
The precursor compounds (Z1,L), in which the leaving group is imidazolyl, triazolyl or benzotriazolyl, can be obtained by the action of their alkaline salt, their trimethylsilyl derivative or their dimethylstannyl derivative on the corresponding halogenated precursor compound, for example according to the following reaction scheme: [CF3SO2NSO(C4H9)]Cl]+ImSi(CH3)3xe2x86x92ClSi(CH3)3+[CF3SO2NSO(C4H9)Im], in which Im represents 
The precursor compounds (Z1,L), in which the leaving group is a pseudohalogen such as a sulfonate, can be obtained by the action of the acid chloride or the anhydride of the sulfonic acid corresponding to the sulfonate, on an abovementioned salt R1xe2x80x94X1(Z1)xe2x80x94Qxe2x80x94X2(O)R2xe2x88x92M+. The reaction of a silver salt with a sulfonyl chloride R7SO2Cl (R7 being of the same nature as the groups Ri) according to the following scheme is particularly advantageous:
R1xe2x80x94X(Z1)xe2x80x94Qxe2x80x94X(O)R2xe2x88x92Ag++R7SO2Clxe2x86x92R1xe2x80x94X(Z1)xe2x80x94Qxe2x80x94X (SO3R7)R2+AgCl
In general, it is advantageous to prepare the precursor compounds R1xe2x80x94X1(Z1)xe2x80x94Qxe2x80x94X2(L)R2 from a compound comprising an anion in which the sulfur or the phosphorus are in the oxidation state IV and III, respectively. On oxidizing these anions, the sulfur VI or phosphorus V derivatives are obtained according to the reaction scheme
R1xe2x80x94X(Z1)xe2x80x94Qxe2x80x94X2(R2)xe2x88x92A++2Lxe2x86x92R1xe2x80x94X(Z1)xe2x80x94Qxe2x80x94X2(L)R2+LA
The preferred compounds for L are halogens, such as fluorine, chlorine or bromine.
The various leaving groups can be exchanged by techniques that are well known to those skilled in the art. For example, the chlorine can be replaced with fluorine by the action of an agent containing active fluoride ions and an affinity for the chlorine ions, such as silver fluoride AgF or tetramethylammonium fluoride, 1,1,1,3,3,3-hexakis(dimethylamino)-diphosphazenium fluoride {[(CH3)2N]3P}2N+Fxe2x88x92 or tetrakis(tris(dimethylamino)-phosphoranylideneaminophosphonium Fluoride {[(CH3)2N]3Pxe2x95x90N}4P+Fxe2x88x92, or the compound of addition of tris(dimethylamino)sulfonium fluoride with trimethylfluorosilane [(CH3)2N]3S+[Si(CH3)3F2]xe2x88x92.
The imidazole or triazole derivatives can be obtained by the action of their alkaline salt or their trimethylsilyl or dimethylstannyl derivative) on the corresponding derivative, according to the reaction scheme:
[CF3SO2NSO(C4H9)Cl]+ImSi(CH3)3xe2x86x92CiSi(CH3)3+[CF3SO2NSO(C4H9)Im]
in which Im represents imidazolyl, triazolyl or benzotriazolyl.
A symmetrical compound, in which X1(Z1) is identical to X2(Z2), can be prepared by the action of an ionic nitride or a metallic derivative of hexamethyl-disilazane or of ammonia in the presence of a base on a precursor containing a leaving group L, according to the following reaction scheme, in which R, X and Z have the meaning given above, respectively, for Ri, Xi and Zi, A and L are as defined above: 2RX(Z)L+A3Nxe2x86x92[RX(Z)]2Nxe2x88x92A++2LA. For example:
2CF3SO(xe2x95x90NSO2CF3)F+Li3Nxe2x86x92[CF3SO(xe2x95x90NSO2CF3)]2Nxe2x88x92A++2LiF
The nitriding agent may advantageously be Li3N, ammonia, its derivatives with silanes and their alkali metal derivatives such as N[SiCH3)3]2Li, N[SiCH3)3]2Na, and N [SiCH3)3]2K.
A compound of formula [R1SO2Nxe2x80x94S*xe2x95x90O(R2)xe2x95x90NSO2R3]xe2x88x92M+ can be obtained by reacting a salt [R1SO2NSO2R2]xe2x88x92 Mxe2x80x2+ with a halogenating agent, to give the precursor R1SO2NSOR2(X) (X being a halogen). Said precursor is then condensed with a sulfonamide R3SO2NH2 in the presence of a base or with its metallic derivatives such as R3SO2NLi2 or R3SO2NNa2. The desired cation for the final compound is obtained by standard ion-exchange processes.
In the same way, the ionic carbides allow the compounds [RX(Z)]3Cxe2x88x92A+ to be prepared, according to the reaction scheme 2RX(Z)L+A4Cxe2x86x92[RX(Z)]3Cxe2x88x92A++3LA.
Given the large possible choice for the substituents which can be present on the anionic group, the compounds of the invention make it possible to induce ionic conduction properties in most organic, liquid or polymeric media containing polarity, even low polarity. The applications are important in the field of electrochemistry, in particular for the storage of energy in primary or secondary generators, in supercapacitors, in fuel cells and in electroluminescent diodes. The compatibility of the ionic compounds of the invention with organic liquids or polymers makes it possible to induce pronounced antistatic properties, even when the content of ionic compound is extremely low. Accordingly, another subject of the present invention consists of an ion conducting material consisting of an ionic compound of the present invention dissolved in a solvent.
The ionic compound used to produce an ion conducting material is preferably chosen from compounds whose cation is ammonium, or a cation derived from a metal, in particular lithium or potassium, zinc, calcium, rare-earth metals, or an organic cation, such as a substituted ammonium, an imidazolium, a triazolium, a pyridinium or a 4-dimethylaminopyridinium, said cations optionally bearing a substituent on the carbon atoms of the ring. The ion conducting material thus obtained has high conductivity and high solubility in solvents, on account of the weak interactions between the positive charge and the negative charge. It has a broad field of electrochemical stability, and it is stable in both reducing and oxidizing media. Furthermore, the compounds which have an organic cation and a melting point below 150xc2x0 C., in particular the compounds containing an imidazolium, triazolium, pyridinium or 4-dimethylaminopyridinium cation, have high intrinsic conductivity, even in the absence of solvent, when they are in the molten state.
The solvent for an ion conducting material of the invention can be an aprotic liquid solvent, a solvating polymer, a polar polymer or a mixture thereof. The aprotic liquid solvent is chosen, for example, from linear ethers and cyclic ethers, esters, nitriles, nitro derivatives, amides, sulfones, sulfolanes, alkylsulfamides and partially hydrogenated hydrocarbons. The solvents which are particularly preferred are diethyl ether, dimethoxyethane, glyme, tetrahydrofuran, dioxane, dimethyltetrahydrofuran, methyl or ethyl formate, propylene or ethylene carbonate, alkylcarbonates (in particular dimethylcarbonate, diethylcarbonate and methyl propyl carbonate), butyrolactones, acetonitrile, benzonitrile, nitromethane, nitrobenzene, dimethylformamide, diethylformamide, N-methylpyrrolidone, dimethyl sulfone, tetramethylene sulfone, tetramethylene sulfone and tetraalkylsulfonamides containing from 5 to 10 carbon atoms.
The solvent for the ion conducting material can be a polar polymer chosen from solvating, crosslinked or non-crosslinked polymers, bearing or not bearing grafted ionic groups. A solvating polymer is a polymer which contains solvating units containing at least one hetero atom chosen from sulfur, oxygen, nitrogen and fluorine. As examples of solvating polymers, mention may be made of polyethers of linear, comb or block structure, forming or not forming a network, based on poly(ethylene oxide), or polymers containing the ethylene oxide or propylene oxide or allyl glycidyl ether unit, polyphosphazenes, crosslinked networks based on polyethylene glycol crosslinked with isocyanates or networks obtained by polycondensation and bearing groups which allow the incorporation of crosslinkable groups. Mention may also be made of block copolymers in which certain blocks bear functions which have redox properties. Needless to say, the above list is not limiting, and any polymer with solvating properties can be used.
An ion conducting material of the present invention can simultaneously comprise an aprotic liquid solvent chosen from the aprotic liquid solvents mentioned above and a polar polymeric solvent comprising units containing at least one hetero atom chosen from sulfur, nitrogen, oxygen and fluorine. It can comprise from 2 to 98% of liquid solvent. As examples of such a polar polymer, mention may be made of polymers mainly containing units derived from acrylonitrile, from vinylidene fluoride, from N-vinylpyrrolidone or from methyl methacrylate. These polymers can bear ionic groups. The proportion of aprotic liquid in the solvent can range from 2% (corresponding to a plasticized solvent) to 98% (corresponding to a gelled solvent). An ion conducting material of the present invention can also contain a salt conventionally used in the prior art for the production of an ion conducting material. Among the salts which can be used as a mixture with an ionic compound according to the invention, the salt most particularly preferred is chosen from perfluoroalkane sulfonates, bis(perfluoroalkylsulfonyl)imides, bis(perfluoro-alkylsulfonyl)methanes and tris(perfluoroalkyl-sulfonyl)methanes.
Needless to say, an ion conducting material of the invention can also contain the additives conventionally used in this type of material, and in particular inorganic or organic fillers in powder or fibre form.
An ion conducting material of the invention can be used as an electrolyte in an electrochemical generator. Another subject of the present invention is thus an electrochemical generator comprising a negative electrode and a positive electrode which are separated by an electrolyte, characterized in that the electrolyte is an ion conducting material as defined above. Preferably, the cation of the ionic compound of the electrolyte is Li+ or K+. According to one specific embodiment, such a generator comprises a negative electrode consisting of lithium metal, or an alloy thereof, optionally in the form of a nanometric dispersion in lithium oxide, or a nitride double salt of lithium and of a transition metal, or an oxide of low potential having the general formula Li1+yTi2xe2x88x92x4O4 (0xe2x89xa6x, yxe2x89xa61) , or carbon and carbon-based products derived from the pyrolysis of organic materials. When the negative electrode functions by exchanging lithium ions, it is particularly advantageous to use, for the electrolyte, a compound of the invention in which the cation is an Li+ ion. According to another embodiment, the generator comprises a positive electrode chosen from vanadium oxides VOx (2xe2x89xa6xxe2x89xa62.5), LiV3O8, LiyNi1xe2x88x92xCoxO2, (0xe2x89xa6x, yxe2x89xa61), magnesium spinels LiyMn1xe2x88x92xMxO2, (M=Cr, Al, V, Ni, 0xe2x89xa6xxe2x89xa60.5; 0xe2x89xa6yxe2x89xa62), organic polydisulfides, FeS, FeS2, iron sulfate Fe2(SO4)3, iron and lithium phosphates and phosphosilicates of olivine structure, or their products of substitution of the iron with manganese, which are used alone or as mixtures. The positive electrode collector is preferably made of aluminium.
An ionic compound of the present invention can also be used to induce an ionic conductivity in media of low polarity, such as aliphatic and aromatic hydrocarbons and media which contain a large fraction thereof, polymers of relatively unpolar and/or hydrophobic nature, and supercritical carbon dioxide.
An ion conducting material of the present invention can also be used in a supercapacitor. Another subject of the present invention is, consequently, a supercapacitor using at least one carbon electrode with a high specific surface, or an electrode containing a redox polymer, in which the electrolyte is an ion conducting material as defined above.
The ionic compounds of the present invention can be used for doping polymers in order to improve their electron conduction. The polymers concerned are essentially polyacetylenes, polyphenylenes, polypyrrols, polythiophenes, polyanilines and polyquinolines which are substituted or unsubstituted, as well as polymers in which the aromatic units are separated by the vinylene unitxe2x80x94CHxe2x95x90CHxe2x80x94. The doping process consists in partially oxidizing the polymer in order to create carbocations whose charge is compensated by the anions in the compounds of the invention. This doping can be carried out chemically or electrochemically, optionally simultaneously with the formation of the polymer. For this specific application, compounds of the invention bearing a highly delocalized charge are preferably chosen, in particular the compounds in which Z is xe2x95x90C(Cxe2x89xa1N)2 xe2x95x90NSO2R or xe2x95x90C(SO2R)2, which impart thermal and mechanical stability properties. The polymers thus doped are another subject of the present invention.
In addition, an ion conducting material of the present invention can be used as an electrolyte in an electrochromic device. An electrochromic device in which the electrolyte is an ion conducting material according to the invention is another subject of the present invention. Such a device also comprises electrodes whose active material is chosen from WO3, MoO3, iridium oxyhydroxides IrOx,Hy, (2xe2x89xa6xxe2x89xa63; 0xe2x89xa6yxe2x89xa63), Prussian blue, viologens and their polymers, and aromatic polyimides.
The compounds of the present invention can be used for the catalysis of various types of chemical reaction, and in particular for polymerization reactions, condensation reactions, addition or elimination reactions, oxidation or reduction reactions, solvolyses, Friedel-Crafts reactions and Diels-Alder reactions. For these applications in catalysis, the compounds will be chosen essentially as a function of the cation associated with the anionic part.
For the catalysis of Diels-Alder reactions or Friedel-Crafts reactions, the cations of an alkali metal, of an alkaline-earth metal, of a transition metal or of a rare-earth metal are suitable. Compounds containing an H+, Li+, Mg++, Ca++, Cu++, Zn++, Al+++, Fe++ or Fe+++ cation are preferred.
The compounds of the invention in which the cation is an onium of the diazonium, sulfonium, iodonium or metallocenium type can be used as cationic polymerization initiators, in particular for polymerizing or crosslinking vinyl ethers, epoxides, acetals and cyclic ethers, vinylamides, oxazolines, isobutylene, styrene or siloxanes. Under the action of actinic radiation, such compounds generate the corresponding acidic form which is capable of initiating a cationic polymerization reaction. A compound of the invention can be used as a photo-initiator optionally in the presence of a sensitizer, or of a radical initiator which can be initiated thermally or by actinic radiation. The compounds of the invention in the form of an amine salt can serve as initiators for cationic polymerizations by heating to release the corresponding protonic form. Similarly, if the cation is a salt of a cationic azo compound (for example as represented below), it can serve, by heating, as an initiator for radical polymerizations. 
The present invention makes it possible to obtain compounds in which the anion has intrinsic chirality, which makes it possible to induce enantiomeric asymmetry during the use of said compounds as catalysts, to prepare stereoregular polymers and to give the materials containing them an optical rotation.